OAKLAND, Calif. -- A federal prosecutor said Wednesday that Noor Salman, the widow of the man who killed 49 people at an Orlando, Fla., nightclub last June, knew that her husband was planning the assault that became one of the deadliest mass shootings in United States history.

''She knew he was leaving that night to do the attack, and her actions contributed to the deaths of 49 people,'' Sara Sweeney, an assistant United States attorney, said during a hearing here in Federal District Court